The present invention has application in conventional endoscopic and open surgical instrumentation as well application in robotic-assisted surgery. The present invention has even further relation to surgical staples and staplers.
In recent years surgery has markedly advanced through the performance of laparoscopic and endoscopic surgical procedures such as cholecystectomies, gastrostomies, appendectomies, and hernia repair. These procedures are accomplished through a trocar assembly, which is a surgical instrument used to puncture a body cavity. The trocar contains a sharpened obturator tip and a trocar tube or cannula. The trocar cannula is inserted into the skin to access the body cavity, by using the obturator tip to penetrate the skin. After penetration, the obturator is removed and the trocar cannula remains in the body. It is through this cannula that surgical instruments are placed. Specifically, it is through this trocar cannula that surgical stapling instruments with cutting mechanisms are placed. One such trocar is the Endopath (copyright) trocar manufactured by ETHICON ENDO-SURGERY, Cincinnati, Ohio.
The application of endoscopic surgical stapling and suturing instruments has been provided in such surgical procedures. One such endoscopic instrument, often referred to as an endocutter, is capable severing tissue and providing hemostasis along both sides of the cut. An example of an endocutter can be found in U.S. Pat. No. 5,673,840 issued on Oct. 7, 1997, which is hereby incorporated herein by reference.
In the case of such an endocutter, the tissue is compressed between a lower jaw and an anvil. The lower jaw holds a cartridge that holds tiny drivers that house U-shaped staples. After the tissue is compressed, axial movement of the firing wedges forces the drivers and staples radially toward the anvil. This movement causes the staples to pierce the compressed tissue and strike curved pockets in the face of the anvil. When the legs of the staples strike the anvil pockets, they buckle from column loading and curl inward in a manner similar in concept to operation of a common office stapler. The anvil pocket geometry causes them to deform inward, forming a B-like shape as the legs of the staples are permanently deformed back on themselves. Often, two triple rows of staples are being simultaneously formed, with a knife following just behind the forming operation to separate the tissue between the two triple rows (lines) of staples. There are a number of problems associated with the forces required to deform the staples and the shape the deformed staple assumes under certain circumstances. The high forces require expensive materials and manufacturing techniques because the jaw and anvil need to be highly strong and rigid. In addition, the high forces require high firing wedge forces. These forces must be generated over the length of the staple line. The resulting total energy input limits the length of staple lines that can be formed by a human using a single hand squeezing motion. Many physicians find it difficult to fire an endocutter.
Furthermore, it is difficult to use a single staple size that can provide hemostasis over a range of tissue thicknesses. With conventional metal staples, the staple legs tend to simply buckle part of the way back from the distal ends. This distal portion remains primarily straight. As a result, when the staples are deformed most extensively for very thin tissue, the straight portions of the staple legs pass beyond the flat base of the staple and the sharp points end up protruding out of the tissue where they can catch and lacerate tissue. If the tissue is very thick and only the distal portions of the staple legs are formed, the staple legs won""t curve back on themselves to form the hook-like geometry required to hold the tissue in place.
In accordance with the present invention, there is provided a surgical staple having first undeployed shape for loading into a stapler, and a second deployed shape for connecting tissue together. The staple has a crown and first and second legs, one attached to each end of the crown. The legs extend from the crown in a direction substantially perpendicular to the longitudinal axis of the crown when the staple is in its first shape. The legs comprise first and second layers of material joined together. The first layer of material is a superelastic alloy having a relaxed configuration substantially in the staple""s second shape. The second layer of material is a linear elastic material having a relaxed configuration substantially in the staple""s first shape. The second layer of material has sufficient rigidity to keep the first layer in the first shape prior to the staple being deployed.